1. Field of the Invention
The present invention relates to a keyboard device used in a keyboard instrument such as an electronic piano or an electronic organ.
2. Description of the Related Art
Conventionally, a keyboard device such as an electronic piano is known where the keys provided on a keyboard chassis have a thin bendable section that bends in an up and down direction and rotate in the up and down direction by bending the bendable section, and hammer members are rotatably provided on the keyboard chassis that apply action load to the keys in response to key pushing operations, as described in Japanese Patent Application Laid-Open (Kokai) Publication No. 05-011747.
In a keyboard device such as this, when the front portion of a key is depressed by a key pushing operation, the key rotates such that its rear portion rises and a portion of the key comes in contact with the hammer member as a fulcrum. Accordingly, the bendable section is pressed upward by the key and bends thereby. On the other hand, when the rear portion of the key is depressed, the key rotates such that the rear portion is lowered and a portion of the key comes in contact with the hammer member as a fulcrum. Accordingly, the bendable section is pressed downward and bends thereby. As a result of this structure, the bendable section significantly bends in the up and down direction according to a depressed portion of the key. Therefore, there is a problem in that repeated stress concentration on the bendable section causes the bendable section to become damaged.
For this reason, in order to prevent damage to the thin bendable section provided in the key, the conventional keyboard device has a structure in which an upper deformation restricting section that restricts elastic deformation of the bendable section in the upward direction and a lower deformation restricting section that restricts elastic deformation of the bendable section in the downward direction are provided on portions of the key that are positioned to the front of the bendable section. A portion of the upper deformation restricting section and a portion of the lower deformation restricting section which comes in contact with the keyboard chassis are formed on the key so as to be shifted from each other in the front-back direction of the key.
In a keyboard device such as this, when the front portion of a key is depressed, the rear portion of the key is pressed upwards with a portion of the key in contact with the hammer member as a fulcrum, and so the upper deformation restricting section of the key comes in contact with the undersurface of the keyboard chassis, whereby the upward elastic deformation of the bendable section is restricted. Also, when the rear portion of the key is depressed, the rear portion of the key is pressed downwards with a portion of the key in contact with the hammer member as a fulcrum, and so the lower deformation restricting section of the key comes in contact with the upper surface of the keyboard chassis, whereby the downward elastic deformation of the bendable section is restricted. As a result, damage to the bendable section can be prevented.
However, in the conventional keyboard device, the portion of the upper deformation restricting section of the key which comes in contact with the undersurface of the keyboard chassis when the front portion of the key is depressed, and the portion of the lower deformation restricting section of the key which comes in contact with the upper surface of the keyboard chassis when the rear portion of the key is depressed are formed to be shifted from each other in the front-back direction of the key, and therefore the rotation fulcrum of the key differs in the front-back direction between when the front portion of the key is depressed and when the rear portion of the key is depressed. Accordingly, there is a problem in that the rotation movement of the keys is not always constant and a sense of incongruity can occur during key pushing operations.
The present invention has been conceived to solve the above-described problems, and an object of the present invention is to provide a keyboard device that holds the rotation fulcrum of a key stable regardless of whether the front portion of the key is being depressed or the rear portion of the key is being depressed, which ensures the durability of the bendable section, stabilizes the rotation movement of the keys and favorably performs key pushing operations.